<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    function foo1(){
        console.log("我在第1层")
        function foo1(){
            console.log("我在第2层")
            function foo1(){
                console.log("我在第3层")

            }
            foo1()
        }
        foo1();
    }



    foo1();
</script>
</body>
</html>